Flotation machine

ABSTRACT

A flotation machine comprising a flotation cell having therein an air inlet pipe for introducing air into the liquid being treated, a rotating body for agitating the liquid, and a dispersing unit having a plurality of guide vanes characterized by the improvement in which projection portions are provided in the flow passages for the liquid formed between the guide vanes.

United States Patent [191 Nagahama [451 Feb. 4, 1975 i 1 FLOTATIONMACHINE [75] Inventor: Tatsuya Nagahama, Tokyo, Japan [73] Assignee:Mitsui Mining & Smelting Co., Ltd,

Tokyo, Japan [22] Filed: Mar. 15, 1973 [21] Appl. No.: 341,675

[30] Foreign Application Priority Data Mar. 18, 1972 Japan.- 47-27602[52] [1.8. Cl 261/87, 209/169, 259/96 [51] Int. Cl B03d l/l6 [58] Fieldof Search 259/7, 8, 23, 24, 107,

[56] References Cited UNITED STATES PATENTS 3,070,229 12/1962 Benozzow,209/169 Nakamura 209/169 Giebel 259/107 Primary Examiner-Harvey C.Hornsby Assistant Examiner--Alan Cantor Attorney, Agent, orFirm-Woodhams, Blanchard & Flynn [57] ABSTRACT A flotation machinecomprising a flotation cell having therein an air inlet pipe forintroducing air into the liquid being treated, a rotating body foragitating the liquid, and a dispersing unit having a plurality of guidevanes characterized'by the improvement in which projection portions areprovided in the flow passages for the liquid formed between the guidevanes.

v 8 Claims, 4 Drawing Figures 1 FLOTATION MACHINE BACKGROUND OF THEINVENTION The flotation machine is required to provide the O function ofgenerating air bubbles in the liquid, or slurry of solids and liquidbeing treated therein. The material desired to be separated from theflotation liquid adheres to the bubbles so that it rises to the surfaceof the tank or cell with the bubbles. Therefore it is desired that theflotation machine be capable of generating a large amount of bubblesbecause the flotation efficiency can be increased in proportion to theamount of generated air bubbles to a certain degree.

Heretofore, the amount of bubbles generated in the cell has beencontrolled to a certain degree by regulating the kind and amount of theflotation agent that is employed. But in general, the amount of bubblesgenerated depends on the amount of air that is introduced into the cell.The amount of air introduced into the cell has heretofore been increasedby increasing the speed of rotation of the agitator or impeller or byblowing in a large amount of air progressively into the cell of theflotation machine. However, when the amount of air introduced into thecell is increased by increasing the speed of rotation of the rotatingbody of the flotation machine, there are the-drawbacks that theconsumption of power is increased and the amount of wear of the rotatingbody and its supporting mechanical structure is increased. When air isblown' progressively into the cell, there is the drawback that extraequipment and power are required for the preparation and supply of thepressurized air.

SUMMARY OF THE INVENTION The present invention is intended to provide animproved flotation machine capable of improving the flo-' tationefficiency by increasing the surface area of the generated air bubbles,but without necessarily increasing the total volume'of air sucked intothe cell.

The inventor has discovered, as a result of numerous studies, that thesurface areaof the bubbles generated by suction of air can be increasedin a flotation machine employing an air suction pipe, such as a standpipe or a hollow shaft, positioned in parallel with the vertical axis ofthe flotation cell, a rotating body for effecting agitation of theflotation liquid and a dispersing unit consisting of a plurality ofguide vanes provided at the bottom portion of the flotation cell. Whenthe relatively small number of relatively large diameter bubbles in theflotation liquid directed from the center of the cell through thedispersing unit and thence toward the side wall of the flotation cellare subdivided into a larger number of smaller diameter bubbles, theefficiency of flotation is enhanced. Particularly when projectingportions are provided between the guide vanes of the dispersing unit,the efficiency of flotation is conspicuously enhanced.

The present invention is based on this discovery.

The present invention will be further described in detail with referenceto the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cut-awayperspective view showing the inside of a cell. I

FIG. 2 is an enlarged, partially cut-away, plan view of the dispersingunit of the FIG. 1.

FIG. 3 is a perspective view ofa guide vane.

FIG. 4 is a perspective view ofa modified guide vane.

DETAILED DESCRIPTION OF THE INVENTION The'structure of the flotationmachine, except for the structure of the guide vanes of the dispersingunit as shown in the drawings is generally similar to that of aconventional flotation machine and it will be described only briefly.

The apparatus comprises a flotation cell 1 having a rotating body orimpeller 2 for drawing air into the cell and circulating the liquidthrough the cell. The impeller 2 is rotated by a shaft 3. An air inletpipe 4 encircles and is spaced from the shaft 3. A stationary dispersingunit 5 is mounted on the lower end of the pipe 4. The dispersing unit 5has a series of guide vanes, such as the vanes 6 and 7. A frothdischarging trough 8 is provided in the side wall of the cell at theupper end thereof. The guide vanes are mounted on support rings 9 and10.

When the impeller 2 is rotated in the direction of the arrow (FIG. 1)after feeding the flotation liquid to the flotation cell 1, air issucked in through the inlet pipe 4. This air flows to the inside of thedispersing unit 5, is mixed with the flotation liquid thereat and thenis di rected between the guide vanes of the dispersing unit 5 toward theside wall of the flotation cell by the rotation of the impeller 2.

As shown in FIG. 2, projecting portions (6', 7) are provided in thepassage formed between the guide vanes. It has been discovered thatthese projectingportions cause the air bubbles to be subdivided so thata larger number of smaller diameter-bubbles are formed, as compared withthe case of the conventional dispers ing unit which has guide vanes madeof curved plates and which do not have any projection portions. That is,by employing the apparatus shown in FIG. 2, the generated air bubblesare subdivided and dispersed in the flotation liquid. The mixture of airbubbles and liquid is discharged from the dispersing unit flowing in asubstantially circumferential direction relative to the side wall of theflotation cell. It is believed that this subdivision effect is obtainedbecause the air bubble-liquid mixture is squeezed as it passes throughthe narrow passages provided by the projecting portions 6', 7 on thevanes 6 and 7. Accordingly, comparing the flotation machine on thepresent invention with the conventional flotation machine, when bothflotation machines are operated in-such a way that the amounts of theair sucked in are substantially equal, in the flotation machine of thepresent invention, a larger number of the smaller diameter air bubblesare formed as discussed in the foregoing, the total surface area of thebubbles is increased, and the amount of the material which adheres' tobubbles is increased. For this reason, the amount of discharge of frothper unit time to the froth discharging trough 8 as shown in FIG. I isalso improved.

As the projecting portions of the dispersing unit to be installed in theflotation machine of the present invention, it is desirable to make theprojecting portions integral with the guide vanes. Particularly it ispreferable to provide the projecting portions onthe leading surface ofthe guide vanes, in the direction of rotation of the impeller, that is,on the otherwise concave sides of the vanes. Also, as the shape of theprojecting portions, there is no particular limitation, but guide vaneshaving a streamline type projecting portions as shown in FIG. 3corresponding to the guide varies in FIG. 2 or the guide vanes 11 havingcolumnar shape projecting portion 11 as shown in FIG. 4 can be employedin the present invention. In the present invention, if the spacingbetween the tip of the projecting portion and the back surface of theguide vane adjacent thereto, namely, the narrowest dimension of the zonebetween adjacent vanes is excessively narrow, the flow of the flotationliquid can be interrupted. Also when it is excessively large, the bubblebreaking and dispersing effects are reduced. It has been foundadvantageous, therefore, to employ projecting portions which occupy atthe narrowest point of said zone, from about 20 to 90 percent of the gapthat would exist between adjacent guide vanes if the vanes were ofconstant wall thickness. v r

' The dispersing unit according to the present invention can beinstalled not only in circular type flotation cells as illustrated, butalso in any type of the flotation.

cell and in any case, similar effects can be obtained.

The invention will be further described with reference to the followingillustrative example. Example Using a flotation machine (a) accordingtothe present invention in FIGS. 1 and 2, and a flotation machine (b)for comparison purposes in which a dispersing unit employing curvedplates of constant wall thickness as the guide vanes, namely, adispersing unit not having the projecting portions on the guide vanes ofthe flotation machine of the present invention, flotations were effectedunder identical conditions. A waste water having a Cu concentration of30 ppm was supplied to each flotation machine and furthermore, ethylxanthate and a frother were added thereto to form precipitates of Cuxanthate. Flotation was effected for minutes.

The floating conditions of each flotation machine (temperature, speed ofrotation of impeller) were identical.

The results were as shown in the following table.

Table 1 Performance Cu concentration Distribution ratio in tailingsafter of Cu Flotation flotation (ppm) machine tailings froth (a)flotation machine accord- 0.5 1.7 98.3 ing to the present invention (b)comparative flotation machine 2.4 8.0 92.0

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. In a flotation machine comprising a flotation cell having an airinlet pipe for introducing air into the liqsages for directing flowof-the air and theliquid from the impeller, the improvement whichcomprises: each guide vane has an integral projecting portion on itsleading side, in the direction of rotation of said impeller, saidportion projecting toward the trailing side of the adjacent leadingguide vane and defining therewith a zone which converges and thendiverges in a direction away from the central opening of the dispersingunit, for causing subdivision of air bubbles in the liquid.

2. A flotation machine according to claim 1, in which said dispersingunit comprises a series of guide vanes which are forwardly curved in thedirection of rotation .of said impeller, said dispersing unit beingstationarily mounted on the lower end of said air inlet pipe andadjacent to the bottom wall of the cell, said dispersing unit beingcoaxial with the axis of the rotation of said impeller.

3. In a flotation machine comprising a flotation cell having an airinlet pipe for introducing air into the liquid being treated, arotatable impeller for mixing the air with the liquid and circulatingsame in the cell, and an annular dispersing unit having a centralopening in which said impeller is disposed and having a series ofcircumferentially spaced guide vanes defining flow passages fordirecting flow of the air and the liquid from the impeller, theimprovement which comprises: each guide vane has a concave-convex shapewith the concave side thereof being the leading side of the vane in thedirection of rotation of said impeller, each guide vane having a memberdisposed in contact with the concave side thereof and extending partwayacross the flow passage defined between said vane and-the convex side ofthe adjacent leading vane, and defining therewith a flow passage zonewhich converges and then diverges in a direction away from the centralopening of the dispersing unit.

4; A flotation machine according to claim 3, in which said dispersingunit comprises a series of guide vanes which are forwardly curved in thedirection of rotation of said impeller, said dispersing unit beingstationarily mounted on the lower end of said air inlet pipe andadjacent to the bottom wall of the cell, said dispersing 'unit beingcoaxial with the axis of rotation of said impeller.

5. In a flotation machine comprising a flotation cell having an airinlet pipe for introducing air into the liquid being treated, arotatable impeller for mixing the air with the liquid and circulatingsame in the cell, and an annular dispersing unit having a centralopening in which said impeller is disposed and having a series ofcircumferentially spaced guide vanes defining flow passages fordirecting flow of the air and the liquid from the impeller, theimprovement which comprises: projecting portions integral or contiguouswith the guide vanes and located thereon between the central opening andthe periphery of said dispersing unit, each portion projecting towardthe opposing surface of the adjacent a guide vane and e'xtending'partwayacross the flow passage defined between said adjacent guide vanes andforming a narrowed zone in said flow passage for causing subdivision ofair bubbles in the liquid, said flow passage being enlarged relative tosaid narrowed zone on opposite sides of said zone.

6. in a flotation machine comprising a flotation cell having an airinlet pipe for introducing air into the liquid being treated, arotatable impeller for mixing the air with the liquid and circulatingsame in the cell,'and an annular dispersing unit having acentral openingin which said impeller is disposed and having a series ofcircumferentially spaced guide vanes defining flow passages fordirecting flow of the air and the liquid from the impeller, theimprovement which comprises: a projecting portion disposed in each ofsaid flow passages between the opposing surfaces of the adjacent guidevanes that define the flow passage, the projecting portion being locatedin the flow passage between and spaced radially from said centralopening and the periphery of said dispersing unit, the projectingportion extending from one side of the flow passage toward the otherside of the flow passage partway across the flow partway toward thetrailing side of the adjacent guide vane.

1. In a flotation machine comprising a flotation cell having an airinlet pipe for introducing air into the liquid being treated, arotatable impeller for mixing the air with the liquid and circulatingsame in the cell, and an annular dispersing unit having a centralopening in which said impeller is disposed and having a series ofcircumferentially spaced guide vanes defining flow passages fordirecting flow of the air and the liquid from the impeller, theimprovement which comprises: each guide vane has an integral projectingportion on its leading side, in the direction of rotation of saidimpeller, said portion projecting toward the trailing side of theadjacent leading guide vane and defining therewith a zone whichconverges and then diverges in a direction away from the central openingof the dispersing unit, for causing subdivision of air bubbles in theliquid.
 2. A flotation machine according to claim 1, in which saiddispersing unit comprises a series of guide vanes which are forwardlycurved in the direction of rotation of said impeller, said dispersingunit being stationarily mounted on the lower end of said air inlet pipeand adjacent to the bottom wall of the cell, said dispersing unit beingcoaxial with the axis of the rotation of said impeller.
 3. In aflotation machine comprising a flotation cell having an air inlet pipefor introducing air into the liquid being treated, a rotatable impellerfor mixing the air with the liquid and circulating same in the cell, andan annular dispersing unit having a central opening in which saidimpeller is dIsposed and having a series of circumferentially spacedguide vanes defining flow passages for directing flow of the air and theliquid from the impeller, the improvement which comprises: each guidevane has a concavo-convex shape with the concave side thereof being theleading side of the vane in the direction of rotation of said impeller,each guide vane having a member disposed in contact with the concaveside thereof and extending partway across the flow passage definedbetween said vane and the convex side of the adjacent leading vane, anddefining therewith a flow passage zone which converges and then divergesin a direction away from the central opening of the dispersing unit. 4.A flotation machine according to claim 3, in which said dispersing unitcomprises a series of guide vanes which are forwardly curved in thedirection of rotation of said impeller, said dispersing unit beingstationarily mounted on the lower end of said air inlet pipe andadjacent to the bottom wall of the cell, said dispersing unit beingcoaxial with the axis of rotation of said impeller.
 5. In a flotationmachine comprising a flotation cell having an air inlet pipe forintroducing air into the liquid being treated, a rotatable impeller formixing the air with the liquid and circulating same in the cell, and anannular dispersing unit having a central opening in which said impelleris disposed and having a series of circumferentially spaced guide vanesdefining flow passages for directing flow of the air and the liquid fromthe impeller, the improvement which comprises: projecting portionsintegral or contiguous with the guide vanes and located thereon betweenthe central opening and the periphery of said dispersing unit, eachportion projecting toward the opposing surface of the adjacent guidevane and extending partway across the flow passage defined between saidadjacent guide vanes and forming a narrowed zone in said flow passagefor causing subdivision of air bubbles in the liquid, said flow passagebeing enlarged relative to said narrowed zone on opposite sides of saidzone.
 6. IN A FLOTATION MACHINE COMPRISING A FLOTATION CELL HAVING ANAIR INLET PIPE FOR INTRODUCING AIR INTO THE LIQUID BEING TREATED, AROTATABLE IMPELLER FOR MIXING THE AIR WITH THE LIQUID AND CIRCULATINGSAME IN THE CELL, AND AN ANNULAR DISPERSING UNIT HAVING A CENTRALOPENING IN WHICH SAID IMPELLER IS DISPOSED AND HAVING A SERIES OFCIRCUMFERENTIALLY SPACED GUIDE VANES DEFINING FLOW PASSAGES FORDIRECTING FLOW OF THE AIR AND THE LIQUID FROM THE IMPELLER, THEIMPROVEMENT WHICH COMPRISES: A PROJECTING PORTION DISPOSED IN EACH OFSAID FLOW PASSAGES BETWEEN THE OPPOSING SURFACES OF THE ADJACENT GUIDEVANES THAT DEFINE THE FLOW PASSAGE, THE PROJECTING PORTION BEING LOCATEDIN THE FLOW PASSAGE BETWEEN AND SPACED RADIALLY FROM SAID CENTRALOPENING AND THE PERIPHERY OF SAID DISPERSING UNIT, THE PROJECTINGPORTION EXTENDING FROM ONE SIDE OF THE FLOW PASSAGE TOWARD THE OTHERSIDE OF THE FLOW PASSAGE PARTWAY ACROSS THE FLOW PASSAGE AND NARROWINGTHE WIDTH OF SAID FLOW PASSAGE, WITH THE WIDTH OF SAID FLOW PASSAGEBEING ENLARGED ON OPPOSITE SIDES OF SAID PROJECTING PORTION.
 7. Aflotation machine as claimed in claim 6, in which said projectingportion is located closer to said central opening than to the peripheryof said dispersing unit.
 8. A flotation machine as claimed in claim 6,in which said projecting portion extends from the leading side of onevane, in the direction of rotation of the impeller, partway toward thetrailing side of the adjacent guide vane.